1. Field of the Invention
The invention relates to a test key structure and a test key group, and more particularly, to a test key structure and a test key group arranged in array.
2. Description of the Prior Art
In semiconductor fabrication, semiconductor devices or integrated circuits (ICs) are continuously tested in every step so as to maintain device quality. Generally, testing circuit and test key structures are fabricated in a scribe line of a wafer or on a monitor wafer simultaneously with the forming of actual or functional devices in the product wafer so that the fabricating processes are stimulated and the quality of the actual devices are checked by providing and electrically connecting the test pads to an external circuit or pins/probes of a probe card in test steps.
Please refer to FIG. 1, which is a schematic drawing illustrating a conventional test key structure. As shown in FIG. 1, a conventional test key structure 100 is positioned on a scribe line 104 of a wafer 102. The test key structure 100 includes a plurality of electronic elements 110, such as transistors for testing. Each of the electronic elements 110 is electrically connected to four pads 122/124/126/128. In detail, the four pads 122/124/126/128 are electrically connected to a source (not shown), a drain (not shown), a gate (not shown), and a body (not shown) of the electronic element 110 by metal wires 130 in sequence. Furthermore, the electronic element 110 of the test key structure 100 and the pads 122/124/126/128 are arranged in a linear pattern on the scribe line 104.
Please refer to FIG. 1 again. It is observed that each electronic element 110 of the test key structure requires four pads 122/124/126/128 that is large enough so that the probe can contact the pads 122/124/126/128 with ease. However, the four large pads 122/124/126/128 occupy large and valuable areas of the wafer 102. More important, since large areas are required to accommodate the large pads, amount of the electronic elements 110 for testing cannot be increased, and thus test sample size cannot be increased either. There is therefore an imperative issue to provide a test key structure with increased sample size.